JDBCUtils.java

package cn.utils;

import java.io.PrintWriter;
import java.sql.Connection;

import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCUtils {
	//定义4个相关属性
	private static String user="root";//用户名
	private static String password="root";//密码
	private static String url="jdbc:mysql://localhost:3306/mall";
	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	//连接数据库，返回Connection
	public static Connection getConnection() {
		try {
			return DriverManager.getConnection(url,user,password);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}
	
	//关闭相关资源
	
	public static void close(ResultSet rs,Statement stm,Connection conn) {
		try {
			if(rs!=null) {				
				rs.close();				
			}
			if(stm!=null) {
				stm.close();
			}
			if(conn!=null) {
				conn.close();
			}
		} catch (SQLException e) {	
			// TODO Auto-generated catch block
			e.printStackTrace();
		}	
	}
	
	
	//调用
	public void testDML() {
		//String username=request.getParameter("username");
		//response.setContentType("text/html;charset=utf-8");
		//request.setCharacterEncoding("utf-8");
		//PrintWriter out = response.getWriter();
		//连接
		Connection conn=JDBCUtils.getConnection();
		String sql="select * from user where username=?";
		//String sql = "insert into admin values(?, ?)";
		//String sql = "update admin set pwd = ? where name = ?";
		//String sql = "delete from admin where name = ?";
		//创建连接对象
		PreparedStatement psm=null;
		ResultSet rs = null;
		
		try {
			//完成sql语句
			psm=conn.prepareStatement(sql);
			psm.setString(1, "admin");
			//执行
			rs = psm.executeQuery();	
			//增改删用这句,下面if也相应改变
			//int count=psm.executeUpdate();
			if(rs.next()) {
				System.out.println("lll");
				//out.write(rs.getString("username"));
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			JDBCUtils.close(rs, psm, conn);
		}
	}
}